As a minor point of interest, I have been using @url import() to include a common CSS theme across a number of keys I own, and Mikau has similarly been providing a free to use CSS theme that way. I felt it was a very nifty feature, allowing common CSS updates to fix display issues for all users and lessening the maintenance effort for someone who just wants a freely available theme.

Just recently I have noticed the keys I own do not have a theme, falling back to the blue BYOND default. It may well be something on my end, but just to rule out possibilities, was a change made to filter these imports out?
Yes, Lummox stopped allowing import to be used as he said here.
In response to Qubic (#1)
That's really very unfortunate. I can fully appreciate the need to protect both general users from XSS attacks (which may be possible on this feature) and more low-tech malicious image swapping though. It'd be nice if we could reconsider this in the future, mind.